A wire electrical discharge machining device is configured as an electrical discharge machining device using a wire as an electrode. Such a wire electrical discharge machining device generates an electrical discharge between a wire electrode and a workpiece (machining target) while supplying the wire electrode (see Patent document 1, 2, or the like).
FIG. 7 is a diagram showing an example of a wire electrode driving system employed in a conventional wire electrical discharge machining device 151. Referring to FIG. 7(a), a source bobbin 153 stores a wire electrode in a wound form. A source bobbin motor 155 applies a back tension to the wire electrode drawn from the source bobbin 153. A bobbin nut 157 is arranged so as to fix the source bobbin 153 to the source bobbin motor 155. The wire electrode drawn from the source bobbin 153 is transferred via a pillow roller 159, a guide roller 161, and a dancer roller 163, and reaches a brake pulley 169 via guide rollers 165 and 167. A brake roller 171 is pressed in contact with the brake pulley 169 such that the wire electrode is pinched between the brake roller 171 and the brake pulley 169, thereby further applying tension to the wire electrode. The brake roller 171 employs a brake motor (hysteresis motor). In contrast, conventionally, the brake pulley 169 includes no brake motor as its built-in component. The wire electrode transferred via the brake pulley 169 is further transferred via the guide rollers 173, 175, and 177, and reaches an electrical discharge machining unit 179. The electrical discharge machining unit 179 includes an upper head 181a and a lower head 181b, and provides electrical discharge machining using a wire electrode.
Referring to FIG. 7B, after the wire electrode is used in the electrical discharge machining, the direction in which the wire electrode is transferred is changed from a vertical direction to a horizontal direction by means of a lower head roller 183. Subsequently, the wire electrode is transferred via a nozzle holder 185, and reaches a winding unit 187. The winding unit 187 includes a pressing roller 189a and a winding roller 189b. The pressing roller 189a and the winding roller 189b eject the wire electrode in a state in which the wire electrode is pinched between them with a constant pressure. Finally, the wire electrode ejected from the winding unit 187 is ejected to a used wire hopper 193.